U.S. patent application number 10/992142 was filed with the patent office on 2006-05-18 for device and method for providing illuminating light using quantum dots.
Invention is credited to Tajul Arosh Baroky, Janet Bee Yin Chua, Kee Yean Ng, Kok Chin Pan, Kheng Leng Tan.
Application Number | 20060103589 10/992142 |
Document ID | / |
Family ID | 36385746 |
Filed Date | 2006-05-18 |
United States Patent
Application |
20060103589 |
Kind Code |
A1 |
Chua; Janet Bee Yin ; et
al. |
May 18, 2006 |
Device and method for providing illuminating light using quantum
dots
Abstract
A device and method for providing illuminating light utilizes
quantum dots to convert at least some of the original light emitted
from a light source of the device to longer wavelength light to
change the color characteristics of the illuminating light. The
quantum dots may be included in the light source, a light panel
and/or an optional interface medium of the device.
Inventors: |
Chua; Janet Bee Yin; (Perak,
MY) ; Pan; Kok Chin; (Penang, MY) ; Ng; Kee
Yean; (Penang, MY) ; Tan; Kheng Leng; (Penang,
MY) ; Baroky; Tajul Arosh; (Penang, MY) |
Correspondence
Address: |
AGILENT TECHNOLOGIES, INC.;INTELLECTUAL PROPERTY ADMINISTRATION, LEGAL
DEPT.
P.O. BOX 7599
M/S DL429
LOVELAND
CO
80537-0599
US
|
Family ID: |
36385746 |
Appl. No.: |
10/992142 |
Filed: |
November 18, 2004 |
Current U.S.
Class: |
345/3.1 |
Current CPC
Class: |
G02B 6/0055 20130101;
G02F 1/133614 20210101; G02B 6/0023 20130101; G02F 2202/108
20130101 |
Class at
Publication: |
345/003.1 |
International
Class: |
G09G 5/00 20060101
G09G005/00 |
Claims
1. A device for providing illuminating light, said device
comprising: a light source that generates original light; a light
panel optically coupled to said light source so that said light
panel produces said illuminating light, said illuminating light
being derived from said original light; and a wavelength-shifting
region optically coupled to said light source, said
wavelength-shifting region including at least one type of quantum
dots to at least convert some of said original light to converted
light, said converted light being a component of said illuminating
light.
2. The device of claim 1 wherein said wavelength-shifting region is
located within said light source.
3. The device of claim 1 wherein said wavelength-shifting region is
located within said light panel.
4. The device of claim 3 wherein said light panel includes a
microstructured lens feature, said wavelength-shifting region being
located within said microstructured lens feature of said light
panel.
5. The device of claim 1 further comprising an interface medium
positioned between said light source and said light panel, said
wavelength-shifting region being located within said interface
medium.
6. The device of claim 1 wherein said wavelength-shifting region
includes non-quantum fluorescent material to converts some of said
original light to second converted light, said second converted
light being another component of said illuminating light.
7. The device of claim 1 wherein said quantum dots have a coating
of selected material.
8. The device of claim 7 wherein said coating of said quantum dots
includes organic caps, quantum dot shells or caps made of glass
material.
9. The device of claim 1 wherein said quantum dots includes one of
CdS, CdSe, CdTe, CdPo, ZnS, ZnSe, ZnTe, ZnPo, MgS, MgSe, MgTe,
PbSe, PbS, PbTe, HgS, HgSe, HgTe, Cd(S.sub.1-xSe.sub.x),
BaTiO.sub.3, PbZrO.sub.3, PbZr.sub.zTi.sub.1-zO.sub.3,
Ba.sub.xSr.sub.1-x, TiO.sub.3, SrTiO.sub.3, LaMnO.sub.3,
CaMnO.sub.3 and La.sub.1-xCa.sub.xMnO.sub.3.
10. The device of claim 1 wherein said wavelength-shifting region
includes silicone, glass, epoxy or a hybrid material of silicone
and epoxy.
11. A method for providing illuminating light, said method
comprising: generating original light; receiving said original
light, including converting at least some of said original light to
converted light using at least one type of quantum dots; and
transmitting one of said original light and said converted light
into a light panel to produce said illuminating light, said
converted light being a component of said illuminating light.
12. The method of claim 11 wherein said receiving and said
converting are performed at a light source that generates said
original light.
13. The method of claim 11 wherein said receiving and said
converting are performed at said light panel.
14. The method of claim 13 wherein said receiving and said
converting are performed at a microstructured lens feature of said
light panel.
15. The method of claim 11 wherein said receiving and said
converting are performed at an interface medium positioned between
a light source of said original light and said light guide.
16. The method of claim 11 wherein said receiving further includes
converting some of said original light to second converted light
using non-quantum fluorescent material, said second converted light
being another component of said illuminating light.
17. A device for providing illuminating light, said device
comprising: a light source emits original light; and a light guide
panel optically coupled to said light source so that said light
guide panel produces said illuminating light, said illuminating
light being derived from said original light; and a
wavelength-shifting region optically coupled to said light source,
said wavelength-shifting region including at least one type of
quantum dots to at least convert some of said original light to
converted light, said converted light being a component of said
illuminating light.
18. The device of claim 17 wherein said wavelength-shifting region
is located within said light guide panel.
19. The device of claim 18 wherein said light guide panel includes
a microstructured lens feature, said wavelength-shifting region
being located within said microstructured-lens feature of said
light guide panel.
20. The device of claim 17 further comprising an interface medium
positioned between said light source and said light guide panel,
said wavelength-shifting region is located within said interface
medium.
Description
BACKGROUND OF THE INVENTION
[0001] Liquid crystal displays (LCDs) require an external
illumination source such as a backlighting device since the LCDs do
not themselves emit light. Traditional backlighting devices include
a narrow fluorescent tube that serves as a light source to input
"white" color light into one of the sides of a light guide panel
(also known as "light pipe panel"), which is positioned behind a
LCD. The light from the fluorescent tube is internally reflected in
the light guide panel and selectively emitted from the top surface
of the wave guide panel toward the LCD, providing illuminating
light for the LCD
[0002] With technological advancements in light emitting diodes
(LEDs), the fluorescent tubes in traditional backlight devices are
being replaced with LEDs. Some of the advantages of LEDs over
fluorescent tubes include longer operating life, lower power
consumption, and smaller in size. However, LEDs generally have
narrow emission spectrum (approximately +/-10 nm). As an example, a
blue InGaN LED may generate light with wavelength of 470 nm +/-10
nm. As another example, a green InGaN LED may generate light with
wavelength of 510 nm +/-10 nm. As another example, a red AlInGaP
LED may generate light with wavelength of 630 nm +/-10 nm. Due to
the narrow-band emission characteristics, different emission types
of monochromatic LEDs (e.g., red, green and blue LEDs) must be used
together in a backlighting device to provide the white color
illuminating light for a LCD. Alternatively, the original light
emitted from monochromatic LEDs must be partially or almost
completely converted to different wavelength light through
photoluminescence, e.g., fluorescence, to provide the white color
illuminating light.
[0003] Between these two approaches for producing white color
illuminating light using monochromatic LEDs, the latter approach is
generally preferred over the former approach. In contrast to the
latter approach of using photoluminescence, the former approach of
using different emission types of LEDs requires a more complex
driving circuitry since the different emission types of LEDs have
different operating voltage requirements. In addition, different
emission types of LEDs tend to degrade differently over their
operating lifetime, which makes color control over an extended
period difficult using this approach.
[0004] A concern with the latter approach of using
photoluminescence is that many of the phosphors that are currently
available to produce white color illuminating light result in
output light having lower-than-optimal Color Rendering Index
(CRI).
[0005] In view of this concern, there is a need for a device and
method for providing white color illuminating light using
photoluminescence that can potentially increase the CRI of the
illuminating light.
SUMMARY OF THE INVENTION
[0006] A device and method for providing illuminating light
utilizes quantum dots to convert at least some of the original
light emitted from a light source of the device to longer
wavelength light to change the color characteristics of the
illuminating light. The quantum dots may be included in the light
source, a light panel and/or an optional interface medium of the
device.
[0007] A device for providing illuminating light in accordance with
an embodiment of the invention comprises a light source that
generates original light, a light panel optically coupled to the
light source so that the light panel produces the illuminating
light, which is derived from the original light, and a
wavelength-shifting region optically coupled to the light source to
receive the original light. The wavelength-shifting region includes
at least one type of quantum dots to at least convert some of the
original light to converted light, which is a component of the
illuminating light.
[0008] A method for providing illuminating light in accordance with
an embodiment of the invention comprises generating original light,
receiving the original light, including converting at least some of
the original light to converted light using at least one type of
quantum dots, and transmitting one of the original light and the
converted light into a light panel to produce the illuminating
light. The converted light is a component of the illuminating
light.
[0009] Other aspects and advantages of the present invention will
become apparent from the following detailed description, taken in
conjunction with the accompanying drawings, illustrated by way of
example of the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of an illumination device in
accordance with an embodiment of the invention.
[0011] FIG. 2 is a partial cross-sectional view of a light panel
and a reflector of the illumination device in accordance with an
embodiment of the invention.
[0012] FIGS. 3A, 3B, 3C and 3D are diagrams of LEDs with different
configurations of a wavelength-shifting region in accordance with
embodiments of the invention.
[0013] FIGS. 4A, 4B, 4C and 4D are diagrams of LEDs with different
configurations of the wavelength-shifting region and a leadframe
having a reflector cup in accordance with embodiments of the
invention.
[0014] FIG. 5A is a perspective view of the illumination device
with the wavelength-shifting region being positioned within an
optional interface medium in accordance with an embodiment of the
invention.
[0015] FIG. 5B is a perspective view of the illumination device
with the wavelength-shifting region being positioned within an
optional interface medium in accordance with another embodiment of
the invention.
[0016] FIG. 6A is a partial cross-sectional view of the light panel
and the reflector of the illumination device in which the
wavelength-shifting region is positioned within the light panel in
accordance with an embodiment of the invention.
[0017] FIG. 6B is a partial cross-sectional view of the light panel
and the reflector of the illumination device in which the
wavelength-shifting region is positioned within the light panel in
accordance with another embodiment of the invention.
[0018] FIG. 7 is a flow diagram of a method for emitting output
light in accordance with an embodiment of the invention.
DETAILED DESCRIPTION
[0019] With reference to FIG. 1, an illumination device 100 in
accordance with an embodiment of the invention is described. The
illumination device 100 can serve as a backlighting device for a
display device that requires external illumination, such as a
liquid crystal display (LCD). As described in more detail below,
the illumination device 100 utilizes at least one type of quantum
dots to provide illuminating light of desired color characteristics
through photoluminescence, for example, "white" color illuminating
light. The illumination device 100 may also utilize one or more
non-quantum fluorescent materials to take advantage of emission
characteristics of the fluorescent materials along with the quantum
dots to produce illuminating light with increased Color Rendering
Index (CRI).
[0020] As shown in FIG. 1, the illumination device 100 includes a
number of light emitting devices 102, a light panel 104, a
reflector 106 and an optional interface medium 108. The light
emitting devices 102 serve as light sources for the illumination
device 100. Although only three light emitting devices are shown in
FIG. 1, the illumination device 100 may include any number of light
emitting devices. Each light emitting device 102 can be any type of
device that generates light, such as a light emitting diode (LEDs)
or a laser diode. As an example, the light emitting devices 102 may
be devices that generate ultraviolet (UV) or blue original
(non-converted) light having a peak wavelength between
approximately 200 nm to 500 nm. The light emitting devices 102 may
include the same type of light emitting devices so that each light
emitting device generates the same original light. As an example,
each of the light emitting devices 102 may be an LED that generates
original light having a peak wavelength of approximately 480 nm.
Alternatively, the light emitting devices 102 may include one or
more different types of light emitting devices so that some of the
light emitting devices may generate different original light from
other light emitting devices.
[0021] As illustrated in FIG. 1, the light emitting devices 102 are
positioned along one side of the light panel 104. Thus, the output
light from the light emitting devices 102 is transmitted into the
light panel 104 through the side 110 of the light panel 104 facing
the light emitting devices 102. In other embodiments, the light
emitting devices 102 may be positioned along more than one side of
the light panel 104.
[0022] The light panel 104 serves to direct the light received at
the side 110 of the light panel from the light emitting devices 102
toward the upper surface 112 of the light panel so that
illuminating light is emitted from the upper surface of light panel
in a substantially uniform manner. In an exemplary embodiment, the
light panel 104 is a light guide panel (also known as "light pipe
panel"). Thus, the light panel 104 will be referred to herein as
the light guide panel. However, in other embodiments, the light
panel 104 may be any optically transparent panel that can emit
illuminating light from a wide surface of the panel using light
from one or more light sources.
[0023] As illustrated in FIG. 2, the light guide panel 104 is
designed such that light that is internally incident on the upper
surface 112 of the light guide panel at large angles with respect
to normal, as illustrated by the arrow 202, is internally
reflected, while light that is internally incident on the upper
surface at smaller angles, as illustrated by the arrow 204, is
transmitted through the upper surface of the light guide panel. The
light guide panel 104 may include a light extraction feature 208 to
diffuse and scatter the light within the light guide panel so that
light is emitted from the upper surface 112 of the light guide
panel more uniformly. The light extraction feature 208 may be
printed, chemical-etched or laser-etched dots on the bottom surface
206 of the light guide panel 104. Alternatively, the light
extraction feature 208 may be a microstructured lens feature, as
illustrated in FIG. 2, formed on the bottom surface 206 of the
light guide panel 104. As shown in FIG. 2, the microstructured lens
feature 208 includes many protrusions 210, which may have V-shaped
cross-sectional profiles, that optimize angles of reflected or
refracted light so that light can be extracted more uniformly from
the upper surface 112 of the light guide panel 104.
[0024] As shown in both FIGS. 1 and 2, the reflector 106 is
positioned below the light guide panel 104. The reflector 106
serves to reflect light emitted out of the bottom surface 206 of
the light guide panel 104 back into the light guide panel so that
the light may be emitted from the upper surface 112 of the light
guide panel.
[0025] As shown in FIG. 1, the optional interface medium 108 is
positioned adjacent to the side 110 of light guide panel 104
between the light emitting devices 102 and the light guide panel.
The interface medium 108 is made of an optically transparent
material, such as plastic or glass material, so that light from the
light emitting devices 102 is transmitted into the side 110 of the
light guide panel 104 through the interface medium. The interface
medium 108 may be configured to disperse the light from the light
emitting devices 102 along the length of the side 110 of the light
guide panel 104 so that the light from the light emitting devices
102 is distributed along the entire side 110 of the light guide
panel.
[0026] As illustrated in FIGS. 1 and 2, the illumination device 100
further includes a wavelength-shifting region 114, which is located
within the light guide panel 104. However, in other embodiments of
the invention, the wavelength-shifting region 114 may be located
within one or more of the light emitting devices 102, within the
light guide panel 104 and/or within the optional interface medium
108, as described in more detail below. The wavelength-shifting
region 114 includes photoluminescent material that converts some or
virtually all of the original light emitted from one or more of the
light emitting devices 102 to longer wavelength light. The
wavelength-shifting region 114 includes a transparent host matrix
116, which may be polymer (formed from liquid or semisolid
precursor material such as monomer), epoxy, silicone, glass or a
hybrid of silicone and epoxy. The photoluminescent material of the
wavelength-shifting region 114 includes quantum dots 118 and may
also include non-quantum fluorescent material 120. The quantum dots
118 converts at least some of the original light generated by the
light emitting devices 102 to converted light, which is eventually
emitted out of the light guide panel 104 as a component of the
illuminating light provided by the device 100. Similarly, the
non-quantum fluorescent material 120 converts at least some of the
original light generated by the light emitting devices 102 to
another converted light, which is again eventually emitted out of
the light guide panel 104 as another component of the illuminating
light provided by the device 100. Thus, the illuminating light is
derived from the original light generated by the light emitting
devices 102.
[0027] The non-quantum fluorescent material 120, which may be
included in the wavelength-shifting region 114, may be one or more
types of non-quantum phosphors, such as Garnet-based phosphors,
Silicate-based phosphors, Orthosilicate-based phosphors,
Thiogallate-based phosphors, Sulfide-based phosphors and
Nitride-based phosphors. The non-quantum phosphors may be phosphor
particles with or without a silica coating. Silica coating on
phosphor particles reduces clustering or agglomeration of phosphor
particles when the phosphor particles are mixed with the host
matrix to form the wavelength-shifting region 114. Clustering or
agglomeration of phosphor particles may produce illuminating light
having a non-uniform color distribution.
[0028] The silica coating may be applied to synthesized phosphor
particles by subjecting the phosphor particles to an annealing
process to anneal the phosphor particles and to remove
contaminants. The phosphor particles are then mixed with silica
powders, and heated in a furnace at approximately 200 degrees
Celsius. The applied heat forms a thin silica coating on the
phosphor particles. The amount of silica on the phosphor particles
may be approximately 1% with respect to the phosphor particles.
Alternatively, the silica coating can be formed on phosphor
particles without applying heat. Rather, silica powder can be added
to the phosphor particles, which adheres to the phosphor particles
due to Van der Waals forces to form a silica coating on the
phosphor particles.
[0029] The non-quantum fluorescent material 120 may alternatively
include one or more organic dyes or any combination of non-quantum
phosphors and organic dyes.
[0030] The quantum dots 118, also known as semiconductor
nanocrystals, included in the wavelength-shifting region 114 are
artificially fabricated devices that confine electrons and holes.
Typical dimensions of quantum dots range from nanometers to few
microns. Quantum dots have a photoluminescent property to absorb
light and re-emit different wavelength light, similar to phosphor
particles. However, the color characteristics of emitted light from
quantum dots depend on the size of the quantum dots and the
chemical composition of the quantum dots, rather than just chemical
composition as phosphor particles. Quantum dots are characterized
by a bandgap smaller than the energy of at least a portion of the
original light emitted from one or more of the light emitting
devices 102.
[0031] The quantum dots 118 included in the wavelength-shifting
region 114 may be quantum dots made of CdS, CdSe, CdTe, CdPo, ZnS,
ZnSe, ZnTe, ZnPo, MgS, MgSe, MgTe, PbSe, PbS, PbTe, HgS, HgSe, HgTe
and Cd(S.sub.1-xSe.sub.x), or made from a metal oxides group, which
consists of BaTiO.sub.3, PbZrO.sub.3, PbZr.sub.zTi.sub.1-zO.sub.3,
Ba.sub.xSr.sub.1-xTiO.sub.3, SrTiO.sub.3, LaMnO.sub.3, CaMnO.sub.3,
La.sub.1-xCa.sub.xMnO.sub.3. The wavelength-shifting region 114
includes at least one type of quantum dots with respect to chemical
composition and size. The type(s) of quantum dots included in the
wavelength-shifting region 114 may partly depend on the wavelength
deficiencies of the non-quantum fluorescent material 120. As an
example, if the non-quantum fluorescent material 120 produces an
output light that is deficient at around 600 nm, then a particular
type of quantum dots can be selected that can produce converted
light at around 600 nm to compensate for the deficiency, which will
increase the CRI of the illuminating light provided by the device
100. The quantum dots 118 included in the wavelength-shifting
region 114 may or may not be coated with a material having an
affinity for the host matrix. The coating passivates the quantum
dots 118 to prevent agglomeration or aggregation to overcome the
Van der Waals binding force between the quantum dots.
[0032] The coating on the quantum dots 118 can be (a) organic caps,
(b) shells or (c) caps made of glass material, such as Si
nanocrystals. Organic caps can be formed on quantum dots using
Ag.sub.2S and Cd(OH).sub.2, which may preferably be passivated with
Cd.sup.2+ at high pH. A surface modification of the quantum dots is
then performed by attaching dyes to the surface of the quantum
dots. As an example, CdSe surface surfactant is labile and can be
replaced by sequential addition of Se.sup.+ and Cd.sup.2+, which
can grow to make a seed (quantum dot) larger. For Cd.sup.2+ rich
surface, the surface can be treated with Ph-Se and an organic
coating is covalently linked to the surface. This isolation of
molecular particles is referred to as "capped". Type of known
capping molecules include Michelle liquids (Fendler),
Tio-terminations (S-based) (Weller-Hamburg), Phosphate termination
(Berwandi-MIT), Nitrogen termination (pyridine, pyrazine) and
Dendron caps (multi-stranded ligands) (Peng).
[0033] Shells are coatings on inner core material (quantum dots).
Generally, coating material that forms the shells can be oxide or
sulfide based. Examples of shell/core are TiO.sub.2/Cds, ZnO/CdSe,
ZnS/Cds and SnO.sub.2/CdSe. For CdSe core, it can also be coated
with ZnS, ZnSe (selenide based) or CdS, which improves the
efficiency of the CdSe dramatically.
[0034] The wavelength-shifting region 114 may include dispersant or
diffusing particles that are distributed throughout the region. The
diffusing particles may be silica, silicon dioxide, aluminum oxide,
barium titanate, and/or titanium oxide. The wavelength-shifting
region 114 may also include adhesion promoter and/or ultraviolet
(UV) inhibitor.
[0035] In some embodiments of the invention, the
wavelength-shifting region 114 may be incorporated into one or more
of the light emitting devices 102, which may be LEDs, as
illustrated in FIGS. 3A, 3B, 3C and 3D. In FIG. 3A, an LED 300A
that includes the wavelength-shifting region 114 in accordance with
an embodiment of the invention is shown. The LED 300A is a
leadframe-mounted LED. The LED 300A includes an LED die 302,
leadframes 304 and 306, a wire 308 and a lamp 310. The LED die 302
is a semiconductor chip that generates light of a particular peak
wavelength. Thus, the LED die 302 is the light source for the LED
300A. Although the LED 300A is shown in FIG. 3A as including a
single LED die, the LED may include multiple LED dies. The LED die
302 may be designed to generate light having a peak wavelength in
the UV or blue wavelength range. The LED die 302 is situated on the
leadframe 304 and is electrically connected to the other leadframe
306 via the wire 308. The leadframes 304 and 306 provide the
electrical power needed to drive the LED die 302. The LED die 302
is encapsulated in the lamp 310, which is a medium for the
propagation of light from the LED die 302. The lamp 310 includes a
main section 312 and an output section 314. In this embodiment, the
output section 314 of the lamp 310 is dome-shaped to function as a
lens. Thus, the light emitted from the LED 300A as output light is
focused by the dome-shaped output section 314 of the lamp 310.
However, in other embodiments, the output section 314 of the lamp
310 may be horizontally planar.
[0036] The lamp 310 of the LED 300A is made of a transparent host
matrix so that light from the LED die 302 can travel through the
lamp and be emitted out of the output section 314 of the lamp. The
host matrix may be polymer (formed from liquid or semisolid
precursor material such as monomer), epoxy, silicone, glass or a
hybrid of silicone and epoxy. In this embodiment, the lamp 310
includes the wavelength-shifting region 114, which is positioned
around the LED die 302. Although the wavelength-shifting region 114
of the lamp 310 is shown in FIG. 3A as being rectangular in shape,
the wavelength-shifting region may be configured in other shapes,
such as a hemisphere, as shown in FIG. 4A. Furthermore, in other
embodiments, the wavelength-shifting region 114 may not be
physically coupled to the LED die 302. Thus, in these embodiments,
the wavelength-shifting region 114 may be positioned elsewhere
within the lamp 310.
[0037] In FIGS. 3B, 3C and 3D, LEDs 300B, 300C and 300D with
alternative configurations for the wavelength-shifting region 114
in accordance with other embodiments of the invention are shown. In
the LED 300B of FIG. 3B, the wavelength-shifting region 114 fills
the entire lamp 310. Thus, the entire lamp 310 of the LED 300B is
the wavelength-shifting region 114. In the LED 300C of FIG. 3C, the
wavelength-shifting region 114 is located at the outer surface of
the lamp 310. In the LED 300D of FIG. 3D, the wavelength-shifting
region 114 is a thin layer coated over the LED die 302. As an
example, the thickness of the wavelength-shifting region 114 in the
LED 300D can be between ten (10) and sixty (60) microns.
[0038] In alternative embodiments, the leadframe of an LED on which
the LED die is positioned may include a reflector cup, as
illustrated in FIGS. 4A, 4B, 4C and 4D. FIGS. 4A-4D show LEDs 400A,
400B, 400C and 400D with different configurations for the
wavelength-shifting region 114 and a leadframe 404 having a
reflector cup 422. The reflector cup 422 provides a depressed
region for the LED die 302 to be positioned so that some of the
light generated by the LED die is reflected away from the leadframe
404 to be emitted from the respective LED as useful output
light.
[0039] As mentioned above, in other embodiments of the invention,
the wavelength-shifting region 114 may be incorporated into the
optional interface medium 108, as illustrated in FIGS. 5A and 5B.
In FIG. 5A, the wavelength-shifting region 114 is located within
the optional interface medium 108 at a major surface 502 that faces
the light emitting devices 102. In an alternative configuration,
the wavelength-shifting region 114 may be located within the
optional interface medium 108 at the other major surface 504 that
faces the light guide panel 104 or at a location between the major
surfaces 502 and 504. In FIG. 5B, the wavelength-shifting region
114 fills the entire optional interface medium 108. Thus, in this
embodiment, the entire interface medium 108 is the
wavelength-shifting region 114.
[0040] In other embodiments of the invention, the
wavelength-shifting region 114 may be incorporated into the light
guide panel 104, as illustrated in FIGS. 2, 6A, 6B and 6C. In FIG.
2, the wavelength-shifting region 114 is located within the light
guide panel 104 at the bottom surface 206. In an alternative
configuration, the wavelength-shifting region 114 may be located
within the light guide panel 104 at the upper surface 112 or at a
location between the upper and lower surfaces 112 and 206. In FIG.
6A, the wavelength-shifting region 114 fills the entire light guide
panel 104. Thus, in this embodiment, the entire light guide panel
104 is the wavelength-shifting region 114. In FIG. 6B, the
wavelength-shifting region 114 is located within the
microstructured lens feature 208 of the wavelength-shifting region.
Alternatively, the wavelength-shifting region 114 may be included
in parts of the protrusions 210 of the microstructured lens feature
208 of the wavelength-shifting region, such as at the surfaces of
the microstructured lens feature.
[0041] A method for providing illuminating light in accordance with
an embodiment of the invention is described with reference to FIG.
7. At block 702, original light is generated. The original light
may be generated by one or more light sources that each includes
one or more LED dies. Next, at block 704, the original light is
received and at least some of the original light is converted to
converted light using at least one type of quantum dots. Next, at
block 706, at least one of the original light and the converted
light is transmitted into a light panel to produce illuminating
light, which includes the converted light as a component.
[0042] Although specific embodiments of the invention have been
described and illustrated, the invention is not to be limited to
the specific forms or arrangements of parts so described and
illustrated. The scope of the invention is to be defined by the
claims appended hereto and their equivalents.
* * * * *